Air filtration media pack, filter element, air filtration media, and methods

ABSTRACT

An air filtration media pack is provided having a plurality of layers of single facer media. The layer of single facer media includes a fluted sheet, a facing sheet, and a plurality of flutes extending between the fluted sheet and the facing sheet and having a flute length extending from a first face of the filtration media pack to a second face of the filtration media pack. A first portion of the plurality of flutes are closed to unfiltered air flowing into the first portion of the plurality of flutes, and a second portion of the plurality of flutes are closed to unfiltered air from flowing out of the second portion of the plurality of flutes so that air passing into one of the first face and the second face of the media pack and out the other of the first face and the second face of the media pack passes through media to provide filtration of the air. The fluted sheet includes repeating internal peaks facing toward the facing sheet and repeating external peaks facing away from the facing sheet. In addition, the fluted sheet can include at least one ridge extending along at least 50% of the flute length between an internal peak and an adjacent external peak. Additional characterizations of an air filtration media pack, air filtration media, and methods of making and using are provided.

This application is a continuation of U.S. application Ser. No.12/012,785 filed Feb. 4, 2008, now U.S. Pat. No. 7,959,702, issued onJun. 14, 2011, which claims the benefit of U.S. Provisional ApplicationSer. No. 60/899,311 filed Feb. 2, 2007, the contents of which are hereinincorporated by reference.

FIELD OF THE INVENTION

The present invention relates to an air filtration media pack that canbe used to form filter elements for cleaning air. The inventionadditionally relates to filter elements, air filtration media, andmethods for manufacturing and using.

BACKGROUND

Fluid streams, such as air and liquid, carry contaminant materialtherein. In many instances, it is desired to filter some or all of thecontaminant materials from the fluid stream. For example, air flowstreams to engines for motorized vehicles or for power generationequipment, gas streams to gas turbine systems and air streams to variouscombustion furnaces, carry particulate contaminants therein that shouldbe filtered. Also liquid streams in engine lube systems, hydraulicsystems, coolant systems or fuel systems, can carry contaminants thatshould be filtered. It is preferred for such systems, that selectedcontaminant material be removed from (or have its level reduced in) thefluid. A variety of fluid filter (air or liquid filter) arrangementshave been developed for contaminant reduction. In general, however,continued improvements are sought.

Z-media generally refers to a type of fluted filtering media where afluid enters flutes on a first face of the media and exits from flutesat a second face of the media. In general, the faces on z-media areprovided on opposite ends of the media. The fluid enters through openflutes on one face and exits through open flutes on the other face. Atsome point between the first face and the second face, the fluid passesfrom one flute to another flute to provide for filtration.

Early forms of z-media were often referred to as corrugated mediabecause the characterization of the media was adopted from thecorrugated box board industry. Corrugated box boards, however, weregenerally designed for carrying a load. Accordingly, flute designs canbe modified away from the standards and sizes from the corrugated boxboard industry to provide improved media performance.

Various disclosures have been provided for modifying the form of theflutes in z-media. For example, U.S. Pat. No. 5,562,825 describescorrugation patterns which utilize somewhat semicircular (in crosssection) inlet flutes adjacent narrow V-shaped (with curved sides) exitflutes are shown (see FIGS. 1 and 3, of U.S. Pat. No. 5,562,825). InU.S. Pat. No. 5,049,326 to Matsumoto et al., circular (in cross-section)or tubular flutes defined by one sheet having half tubes attached toanother sheet having half tubes, with flat regions between the resultingparallel, straight, flutes are shown. See FIG. 2 of U.S. Pat. No.5,049,326. U.S. Pat. No. 4,925,561 to Ishii et al. (FIG. 1) shows flutesfolded to have a rectangular cross section, in which the flutes taperalong their lengths. In WO 97/40918 (FIG. 1), flutes or parallelcorrugations which have a curved, wave patterns (from adjacent curvedconvex and concave troughs) but which taper along their lengths (andthus are not straight) are shown. Also, in WO 97/40918 flutes which havecurved wave patterns, but with different sized ridges and troughs, areshown.

SUMMARY

An air filtration media pack is provided according to the presentinvention. The air filtration media pack includes a plurality of layersof single facer media. A layer of single facer media comprises a flutedsheet, a facing sheet, and a plurality of flutes extending between thefluted sheet and the facing sheet and having a flute length extendingfrom a first face of the filtration media pack to a second face of thefiltration media pack. A first portion of the plurality of flutes areclosed to unfiltered air flowing into the first portion of the pluralityof flutes, and a second portion of the plurality of flutes are closed tounfiltered air flowing out of the second portion of the plurality offlutes so that air passing into one of the first face and the secondface of the media pack and out the other of the first face and thesecond face of the media pack passes through media to provide filtrationof the air. The fluted sheet includes repeating internal peaks facingtoward the facing sheet and repeating external peaks facing away fromthe facing sheet. In addition, the fluted sheet includes a repeatingpattern of flutes comprising a flute having at least one ridge extendingalong at least a portion of the flute length between an internal peakand an adjacent external peak. Preferably, the repeating pattern offlutes comprises a flute having at least one ridge extending at least50% of the flute length between an internal peak and adjacent externalpeak.

The repeating patter of flutes can comprise any number of flutes wherethe pattern repeats itself. The number of flutes can include one flute,two flutes, three flutes, four flutes, etc. At a location within therepeating pattern, there is at least one ridge extending between aninternal peak and an adjacent external peak. It is possible that thereis a ridge extending between every internal peak and adjacent externalpeak, but that is not necessary. A repeating pattern may include flutesor portions of flutes that do not include a ridge extending between aninternal peak and an adjacent external peak. In the case where thefluted sheet includes a flute having a ridge extending between aninternal peak and an adjacent external peak for a flute period, thatflute period can be referred to as having a “low contact” shape. Whenthe fluted sheet includes two ridges extending between an internal peakand an adjacent external peak for a flute period, the shape of the fluteperiod can be referred to as “zero strain.” While it is desirable toprovide a ridge extending between every adjacent peak, that is notnecessary. It is possible that the repeating pattern has one or moreridge extending between adjacent peaks, and one or more area betweenadjacent peaks that do not include a ridge.

To obtain the benefit of having a ridge extend between adjacent peaks,it can be desirable to have the ridge extend a length of at least 20% ofthe flute length. Preferably, the ridge extends at least 40% of theflute length, at least 50% of the flute length, or at least 80% of theflute length.

An air filtration media pack is provided according to the presentinvention that can be characterized as z-media containing flutes whereinthe flutes contain an enhanced amount of media between adjacent flutes.Techniques for characterizing the amount of filtration media betweenadjacent peaks include reference to a cord-media percentage andreference to a flute width height ratio. For a filtration media packaccording to the invention, the cord-media percentage can be at leastabout 6.2% and the flute width height ratio can be greater than about2.2 or less than about 0.45. In addition, the filtration media packaccording to the invention can be characterized as having a volume onone side of the media pack that is greater than a volume on another sideof the media pack by at least 10%, and wherein the flute width heightratio can be greater than about 2.2 or less than about 0.45.

A fluted media sheet is provided according to the present invention. Thefluted media sheet includes a repeating pattern of flutes comprisinginternal peaks and external peaks. The repeating pattern of flutesincludes at least one ridge extending along at least 50% of a flutelength between an internal peak and an adjacent external peak. The mediacomprises a cellulose based media for fluid filtration.

Methods for forming the air filtration media pack and for using the airfiltration media pack are provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary, schematic, perspective view of an exemplaryz-filtration media according to the prior art.

FIG. 2 is an enlarged schematic, cross-sectional view of a portion ofthe prior art media depicted in FIG. 1.

FIG. 3 is a schematic view of various corrugated media definitions.

FIGS. 4 a-c are enlarged schematic, cross-sectional views of a portionof media illustrating the width height ratio.

FIGS. 5 a-c are enlarged schematic, cross-sectional views of a portionof media according to the present invention.

FIG. 6 is a photograph showing an end view of wound filtration mediaaccording to FIG. 5 a.

FIG. 7 is a photograph showing a perspective view of dust loaded intothe filtration media shown in FIG. 6 wherein a portion of the flutedsheet is peeled back to reveal a dust cake.

FIG. 8 is a perspective view of a tapered fluted sheet of the mediaaccording to FIG. 5 b.

FIGS. 9 a and 9 b are a series of sectional views of a tapered mediaaccording to FIGS. 5 b and 5 c.

FIGS. 10 a and 10 b are enlarged schematic, cross-sectional views of aportion of asymmetric media according to the present invention.

FIG. 11 is a cross-sectional view of a flute after contact with aninverter wheel and before contact with a folder wheel for closure of theflute.

FIG. 12 is a cross-sectional view of a flute taken along line 12-12 ofFIG. 11.

FIG. 13 is a cross-sectional view of a flute taken along line 13-13 ofFIG. 9.

FIG. 14 is a cross-sectional view of a flute after contact with a folderwheel.

FIG. 15 is a cross-sectional view of a flute taken alone line 15-15 ofFIG. 14.

FIG. 16 is a cross-sectional view of a flute taken along line 16-16 ofFIG. 14.

FIG. 17 is a cross-sectional view of a flute taken along line 17-17 ofFIG. 14.

FIG. 18 is an end view of a folded flute depicted in FIG. 14.

FIG. 19 is a sectional view of an exemplary air cleaner that can includea filter element containing the air filtration media pack according tothe present invention.

FIG. 20 is a partial, sectional view of a filter element containing anair filtration media pack according to the present invention.

FIG. 21 is a perspective view of a filter element containing an airfiltration media pack according to the present invention.

FIG. 22 is a perspective view of a filter element containing an airfiltration media pack according to the present invention.

FIG. 23 is a bottom, perspective view of the filter element of FIG. 22.

FIG. 24 is a side view of the sensor board of the filter element ofFIGS. 22 and 23.

FIG. 25 is a partial, sectional view of a filter arrangement containingan air filtration media pack according to the present invention.

FIG. 26 is a partial, sectional view of an air cleaner having a filterelement containing an air filtration media pack according to the presentinvention.

FIG. 27 is a perspective view of an exemplary filter element containingan air filtration media pack according to the present invention.

FIG. 28 is a perspective view of an exemplary filter element containingan air filtration media pack according to the present invention.

DETAILED DESCRIPTION

Fluted Filtration Media

Fluted filtration media can be used to provide fluid filterconstructions in a variety of manners. One well known manner is as az-filter construction. The terms “z-filter construction” or “z-filtermedia” as used herein, is meant to refer to a filter construction inwhich individual ones of corrugated, folded, pleated, or otherwiseformed filter flutes are used to define longitudinal filter flutes forfluid flow through the media; the fluid flowing along the flutes betweeninlet and outlet flow ends (or flow faces) of the media. Some examplesof z-filter media are provided in U.S. Pat. Nos. 5,820,646; 5,772,883;5,902,364; 5,792,247; 5,895,574; 6,210,469; 6,190,432; 6,350,296;6,179,890; 6,235,195; Des. 399,944; Des. 428,128; Des. 396,098; Des.398,046; and, Des. 437,401; each of these fifteen cited references beingincorporated herein by reference.

One type of z-filter media utilizes two media components joined togetherto form the media construction. The two components are: (1) a fluted(for example, corrugated) media sheet; and, (2) a facing media sheet.The facing media sheet is typically non-corrugated, however it can becorrugated, for example perpendicularly to the flute direction asdescribed in International Publication No. WO 2005/077487, publishedAug. 25, 2005, incorporated herein by reference. Alternatively, thefacing sheet can be a fluted (for example, corrugated) media sheet andthe flutes or corrugations may be aligned with or at angles to thefluted media sheet. Although the facing media sheet can be fluted orcorrugated, it can be provided in a form that is not fluted orcorrugated. Such a form can include a flat sheet. When the facing mediasheet is not fluted, it can be referred to as a non-fluted media sheetor as a non-fluted sheet.

The type of z-filter media that utilizes two media components joinedtogether to form the media construction wherein the two components are afluted media sheet and a facing media sheet can be referred to as asingle facer media. In certain z-filter media arrangements, the singlefacer media (the fluted media sheet and the facing media sheet),together, can be used to define media having parallel inlet and outletflutes. In some instances, the fluted sheet and non-fluted sheet aresecured together and are then coiled to form a z-filter mediaconstruction. Such arrangements are described, for example, in U.S. Pat.No. 6,235,195 and U.S. Pat. No. 6,179,890, each of which is incorporatedherein by reference. In certain other arrangements, some non-coiledsections of fluted media secured to flat media, are stacked on oneanother, to create a filter construction. An example of this isdescribed in FIG. 11 of U.S. Pat. No. 5,820,646, incorporated herein byreference. In general, arrangements where the z-filter media is coiledcan be referred to as coiled arrangements, and arrangements where thez-filter media is stacked can be referred to as stacked arrangements.Filter elements can be provided having coiled arrangements or stackedarrangements.

Typically, coiling of the fluted sheet/facing sheet combination (e.g.,the single facer media) around itself, to create a coiled media pack, isconducted with the facing sheet directed outwardly. Some techniques forcoiling are described in International Publication No. WO 2004/082795,published Sep. 30, 2004, incorporated herein by reference. The resultingcoiled arrangement generally has, as the outer surface of the mediapack, a portion of the facing sheet, as a result.

The term “corrugated” used herein to refer to structure in media, ismeant to refer to a flute structure resulting from passing the mediabetween two corrugation rollers, i.e., into a nip or bite between tworollers, each of which has surface features appropriate to cause acorrugation affect in the resulting media. The term “corrugation” is notmeant to refer to flutes that are formed by techniques not involvingpassage of media into a bite between corrugation rollers. However, theterm “corrugated” is meant to apply even if the media is furthermodified or deformed after corrugation, for example by the foldingtechniques described in PCT WO 04/007054, published Jan. 22, 2004,incorporated herein by reference.

Corrugated media is a specific form of fluted media. Fluted media ismedia which has individual flutes (for example, formed by corrugating orfolding or pleating) extending thereacross. Fluted media can be preparedby any technique that provides the desired flute shapes. Corrugating canbe a useful technique for forming flutes having a particular size. Whenit is desirable to increase the height of the flutes (the height is theelevation between peaks), corrugating techniques might not be practicaland it may be desirable to fold or pleat the media. In general, pleatingof media can be provided as a result of folding the media. An exemplarytechnique for folding the media to provide pleats includes scoring andusing pressure to create the fold.

Filter element or filter cartridge configurations utilizing z-filtermedia are sometimes referred to as “straight through flowconfigurations” or by variants thereof. In general, in this context whatis meant is that the serviceable filter elements generally have an inletflow end (or face) and an exit flow end (or face), with flow enteringand exiting the filter cartridge in generally the same straight throughdirection. The term “straight through flow configuration” disregards,for this definition, air flow that passes out of the media pack throughthe outermost wrap of facing media. In some instances, each of the inletflow end and outlet flow end can be generally flat or planar, with thetwo parallel to one another. However, variations from this, for examplenon-planar faces, are possible in some applications. Furthermore, thecharacterization of an inlet flow face and an opposite exit flow face isnot a requirement that the inlet flow face and the outlet flow face areparallel. The inlet flow face and the exit flow face can, if desired, beprovided as parallel to each other. Alternatively, the inlet flow faceand the outlet flow face can be provided at an angle relative to eachother so that the faces are not parallel. In addition, non-planar facescan be considered non-parallel faces.

A straight through flow configuration is, for example, in contrast tocylindrical pleated filter cartridges of the type shown in U.S. Pat. No.6,039,778, in which the flow generally makes a substantial turn as itspasses through the serviceable cartridge. That is, in a U.S. Pat. No.6,039,778 filter, the flow enters the cylindrical filter cartridgethrough a cylindrical side, and then turns to exit through an end facein a forward-flow system. In a reverse-flow system, the flow enters theserviceable cylindrical cartridge through an end face and then turns toexit through a side of the cylindrical filter cartridge. An example ofsuch a reverse-flow system is shown in U.S. Pat. No. 5,613,992.

The filter element or filter cartridge can be referred to as aserviceable filter element or filter cartridge. The term “serviceable”in this context is meant to refer to a media containing filter cartridgethat is periodically removed and replaced from a corresponding aircleaner. An air cleaner that includes a serviceable filter element orfilter cartridge is constructed to provide for the removal andreplacement of the filter element or filter cartridge. In general, theair cleaner can include a housing and an access cover wherein the accesscover provides for the removal of a spent filter element and theinsertion of a new or cleaned (reconditioned) filter element.

The term “z-filter media construction” and variants thereof as usedherein, without more, is meant to refer to any or all of: a single facermedia containing a fluted media sheet and a facing media sheet withappropriate closure to inhibit air flow from one flow face to anotherwithout filtering passage through the filter media; and/or, a singlefacer media that is coiled or stacked or otherwise constructed or formedinto a three dimensional network of flutes; and/or, a filterconstruction including a single facer media; and/or, a fluted mediaconstructed or formed (e.g., by folding or pleating) into a threedimensional network of flutes. In general, it is desirable to provide anappropriate flute closure arrangement to inhibit unfiltered air thatflows in one side (or face) of the media from flowing out the other side(or face) of the media as part of the filtered air stream leaving themedia. In many arrangements, the z-filter media construction isconfigured for the formation of a network of inlet and outlet flutes,inlet flutes being open at a region adjacent an inlet face and beingclosed at a region adjacent an outlet face; and, outlet flutes beingclosed adjacent an inlet face and being open adjacent an outlet face.However, alternative z-filter media arrangements are possible, see forexample US 2006/0091084 A1, published May 4, 2006 to Baldwin Filters,Inc. also comprising flutes extending between opposite flow faces, witha seal arrangement to prevent flow of unfiltered air through the mediapack. In many z-filter constructions according to the invention,adhesive or sealant can be used to close the flutes and provide anappropriate seal arrangement to inhibit unfiltered air from flowing fromone side of the media to the other side of the media. Plugs, folds ofmedia, or a crushing of the media can be used as techniques to provideclosure of flutes to inhibit the flow of unfiltered air from one side ofthe media (face) to the other side of the media (face).

An alternative z-filter construction can be provided utilizing a flutedmedia sheet. For example, the fluted media sheet can be folded to createclosures at the inlet flow face and exit flow face. An example of thistype of arrangement can be seen in, for example, U.S. 2006/0151383 toAAF-McQuay Inc. and WO 2006/13271 to Fleetguard, Inc., that describefluted media having folds or bends perpendicular to the flute directionto seal the ends of the flutes.

Referring to FIG. 1, an exemplary type of media 1 useable as z-filtermedia is shown. Although the media 1 is representative of prior artmedia, many of the terms relied upon for describing the media 1 can alsodescribe portions of the media according to the invention. The media 1is formed from a fluted (in the example corrugated) sheet 3 and a facingsheet 4. In general, the fluted corrugated sheet 3 is of a typegenerally characterized herein as having a regular, curved, wave patternof flutes or corrugations 7. The term “wave pattern” in this context, ismeant to refer to a flute or corrugated pattern of alternating troughs 7b and hills 7 a. The term “regular” in this context is meant to refer tothe fact that the pairs of troughs and hills (7 b, 7 a) alternate withgenerally the same repeating corrugation (or flute) shape and size.(Also, typically in a regular configuration each trough 7 b issubstantially an inverse of each hill 7 a.) The term “regular” is thusmeant to indicate that the corrugation (or flute) pattern comprisestroughs and ridges with each pair (comprising an adjacent trough andridge) repeating, without substantial modification in size and shape ofthe corrugations along at least 70% of the length of the flutes. Theterm “substantial” in this context, refers to a modification resultingfrom a change in the process or form used to create the corrugated orfluted sheet, as opposed to minor variations from the fact that themedia sheet forming the fluted sheet 3 is flexible. With respect to thecharacterization of a repeating pattern, it is not meant that in anygiven filter construction, an equal number of ridges and troughs isnecessarily present. The media 1 could be terminated, for example,between a pair comprising a hill and a trough, or partially along a paircomprising a hill and a trough. (For example, in FIG. 1 the media 2depicted in fragmentary has eight complete hills 7 a and seven completetroughs 7 b.) Also, the opposite flute ends (ends of the troughs andhills) may vary from one another. Such variations in ends aredisregarded in these definitions, unless specifically stated. That is,variations in the ends of flutes are intended to be covered by the abovedefinitions.

In the context of fluted filtration media, and in particular theexemplary media 1, the troughs 7 b and hills 7 a can be characterized aspeaks. That is, the highest point of the hills 7 a can be characterizedas peaks and the lowest points of the troughs 7 b can be characterizedas peaks. The combination of the fluted sheet 3 and the facing sheet 4can be referred to as the single facer media 5. The peaks formed at thetroughs 7 b can be referred to as internal peaks because they facetoward the facing sheet 3 of the single facer media 5. The peaks formedat the hills 7 a can be characterized as external peaks because theyface away from the facing sheet 3 forming the single facer media 5. Forthe single facer media 5, the fluted sheet 3 includes repeating internalpeaks at 7 b that face toward the facing sheet 4, and repeating externalpeaks at hills 7 a that face away from the facing sheet 4.

The term “regular” when used to characterize a flute pattern is notintended to characterize media that can be considered “tapered.” Ingeneral, a taper refers to a reduction or an increase in the size of theflute along a length of the flute. In general, filtration media that istapered can exhibit a first set of flutes that decrease in size from afirst end of the media to a second end of the media, and a second set offlutes that increase in size from the first end of the media to thesecond end of the media. In general, a tapered pattern is not considereda regular pattern. It should be understood, however, that z-media cancontain regions that are considered regular and regions that areconsidered non-regular along the flute length. For example, a first setof flutes may be considered regular along a distance of the flutelength, such as, one quarter the distance to three quarters thedistance, and then for the remaining amount of the flute length can beconsidered non-regular as a result of the presence of a taper. Anotherpossible flute configuration is to have a tapered-regular-taperedarrangement where, for example, a flute tapers from a first face to apre-selected location, the flute then can be considered regular until asecond pre-determined location, and then the flute tapers to the secondface. Another alternative arrangement can be provided as aregular-taper-regular arrangement, or as a regular-taper arrangement.Various alternative arrangements can be constructed as desired.

In the context of z-media, there are generally two types of “asymmetry.”One type of asymmetry is referred to as area asymmetry, and another typeof asymmetry is referred to as volume asymmetry. In general, areaasymmetry refers to an asymmetry in flute cross-sectional area, and canbe exhibited by tapered flutes. For example, area asymmetry exists if afluted area at one location along the length of a flute is differentfrom the fluted area at another location along the length of the flute.The fluted area refers to the area between the fluted sheet and thefacing sheet. Because tapered flutes exhibit a decrease in size from afirst location, e.g., end, to a second location (e.g., end) of the mediapack or an increase in size from a first location (e.g., end) to asecond location (e.g., end) of the media pack, there is an areaasymmetry. This asymmetry (e.g., area asymmetry) is a type of asymmetryresulting from tapering and, as a result, media having this type ofasymmetry can be referred to as non-regular. Another type of asymmetrycan be referred to as volume asymmetry, and will be explained in moredetail. Volumetric asymmetry refers to a difference between a dirty sidevolume and a clean side volume within the filter media pack. Mediaexhibiting volume asymmetry can be characterized as regular if the wavepattern is regular, and can be characterized as non-regular if the wavepattern is non-regular.

Z-media can be provided where at least a portion of the flutes areclosed to the passage of unfiltered air by a technique other thanproviding a plug of adhesive or sealant. For example, the ends of flutescan be folded or crushed to provide a closure. One technique forproviding a regular and consistent fold pattern for closing flutes canbe referred to as darting. Darted flutes or darting generally refers tothe closure of a flute wherein the closure occurs by indenting the fluteand folding the flute to create a regular fold pattern to collapse theflutes toward the facing sheet to provide a closure rather than bycrushing. Darting generally implies a systematic approach to closing theends of flutes as a result of folding portions of the flute so that theflute closures are generally consistent and controlled. For example,U.S. Patent Publication No. US 2006 0163150 A1 discloses flutes having adarted configuration at the ends of the flutes. The darted configurationcan provide advantages including, for example, a reduction in the amountof sealant needed to provide a seal, an increased security in theeffectiveness of the seal, and a desirable flow pattern over the dartedend of the flutes. Z-media can include flutes having darted ends, andthe entire disclosure of U.S. Patent Publication No. US 2006 0163150 A1is incorporated herein by reference. It should be understood that theexistence of darts at the ends of flutes does not render the medianon-regular.

In the context of the characterization of a “curved” wave pattern, theterm “curved” is meant to refer to a pattern that is not the result of afolded or creased shape provided to the media, but rather the apex ofeach hill 7 a and the bottom of each trough 7 b is formed along aradiused curve. Although alternatives are possible, a typical radius forsuch z-filter media would be at least 0.25 mm and typically would be notmore than 3 mm. Media that is not curved, by the above definition, canalso be useable. For example, it can be desirable to provide peakshaving a radius that is sufficiently sharp so that it is not considered“curved.” The radius can be less than 0.25 mm, or less than 0.20 mm. Inorder to reduce masking, it can be desirable to provide the peak with aknife edge. The ability to provide a knife edge at the peak can belimited by the equipment used to form the media, the media itself, andthe conditions under which the media is subjected. For example, it isdesirable to not cut or tear the media. Accordingly, using a knife edgeto create the peak can be undesirable if the knife edge causes a cut ortear in the media. Furthermore, the media can be too light or too heavyto provide a sufficiently non-curved peak without cutting or tearing.Furthermore, the humidity of the air during processing can be enhancedto help create a tighter radius when forming the peak.

An additional characteristic of the particular regular, curved, wavepattern depicted in FIG. 1, for the corrugated sheet 3, is that atapproximately a midpoint 30 between each trough 7 b and each adjacenthill 7 a, along most of the length of the flutes 7, is located atransition region where the curvature inverts. For example, viewing backside or face 3 a, FIG. 1, trough 7 b is a concave region, and hill 7 ais a convex region. Of course when viewed toward front side or face 3 b,trough 7 b of side 3 a forms a hill; and, hill 7 a of face 3 a, forms atrough. In some instances, region 30 can be a straight segment, insteadof a point, with curvature inverting at ends of the segment 30.

A characteristic of the particular regular, curved, wave patterncorrugated sheet 3 shown in FIG. 1, is that the individual corrugationsare generally straight. By “straight” in this context, it is meant thatthrough at least 50% and preferably at least 70% (typically at least80%) of the length between edges 8 and 9, the hills 7 a and troughs 7 bdo not change substantially in cross-section. The term “straight” inreference to corrugation pattern shown in FIG. 1, in part distinguishesthe pattern from the tapered flutes of corrugated media described inFIG. 1 of WO 97/40918 and PCT Publication WO 03/47722, published Jun.12, 2003, incorporated herein by reference. The tapered flutes of FIG. 1of WO 97/40918, for example, would be a curved wave pattern, but not a“regular” pattern, or a pattern of straight flutes, as the terms areused herein.

Referring to the present FIG. 1 and as referenced above, the media 2 hasfirst and second opposite edges 8 and 9. For the example shown, when themedia 2 is coiled and formed into a media pack, in general edge 9 willform an inlet end for the media pack and edge 8 an outlet end, althoughan opposite orientation is possible in some applications.

In the example shown, adjacent edge 8 is provided sealant, in thisinstance in the form of a sealant bead 10, sealing the fluted sheet 3and the facing sheet 4 together. Bead 10 will sometimes be referred toas a “single facer” bead, since it is a bead between the corrugatedsheet 3 and the facing sheet 4, which forms the single facer media 5.Sealant bead 10 seals closed individual flutes 11 adjacent edge 8, topassage of air therefrom.

In the example shown, at adjacent edge 9 is provided sealant, in thisinstance in the form of a sealant bead 14. Sealant bead 14 generallycloses flutes 15 to passage of unfiltered fluid therethrough, adjacentedge 9. Bead 14 would typically be applied as the media 2 is coiledabout itself, with the corrugated sheet 3 directed to the inside. Thus,bead 14 will form a seal between a back side 17 of facing sheet 4, andside 18 of the fluted sheet 3. The bead 14 will sometimes be referred toas a “winding bead” since it is typically applied, as the strip 2 iscoiled into a coiled media pack. If the media 2 is cut in strips andstacked, instead of coiled, bead 14 would be a “stacking bead.”

Referring to FIG. 1, once the media 1 is incorporated into a media pack,for example by coiling or stacking, it can be operated as follows.First, air in the direction of arrows 12, would enter open flutes 11adjacent end 9. Due to the closure at end 8, by bead 10, the air wouldpass through the media shown by arrows 13. It could then exit the mediapack, by passage through open ends 15 a of the flutes 15, adjacent end 8of the media pack. Of course operation could be conducted with air flowin the opposite direction.

In more general terms, z-filter media comprises fluted filter mediasecured to facing filter media, and configured in a media pack of flutesextending between first and second opposite flow faces. A sealant orseal arrangement is provided within the media pack, to ensure that airentering flutes at a first upstream face cannot exit the media pack froma downstream face, without filtering passage through the media.Alternately stated, a z-filter media is closed to passage of unfilteredair therethrough, between the inlet face and the outlet flow face,typically by a sealant arrangement or other arrangement. An additionalalternative characterization of this is that a first portion of theflutes are closed or sealed to prevent unfiltered air from flowing intothe first portion of flutes, and a second portion of the flutes areclosed or sealed to prevent unfiltered air from flowing out of thesecond portion of flutes so that air passing into one of the first faceand the second face of the media pack and out the other of the firstface and the second face of the media pack passes through media toprovide filtration of the air.

For the particular arrangement shown herein in FIG. 1, the parallelcorrugations 7 a, 7 b are generally straight completely across themedia, from edge 8 to edge 9. Straight flutes or corrugations can bedeformed or folded at selected locations, especially at ends.Modifications at flute ends for closure are generally disregarded in theabove definitions of “regular,” “curved” and “wave pattern.”

In general, the filter media is a relatively flexible material,typically a non-woven fibrous material (of cellulose fibers, syntheticfibers or both) often including a resin therein, sometimes treated withadditional materials. Thus, it can be conformed or configured into thevarious fluted, for example corrugated, patterns, without unacceptablemedia damage. Also, it can be readily coiled or otherwise configured foruse, again without unacceptable media damage. Of course, it must be of anature such that it will maintain the desired fluted (for examplecorrugated) configuration, during use.

In the corrugation or fluting process, an inelastic deformation iscaused to the media. This prevents the media from returning to itsoriginal shape. However, once the tension is released the flutes orcorrugations will tend to spring back, recovering only a portion of thestretch and bending that has occurred. The facing sheet is sometimestacked to the fluted sheet, to inhibit this spring back in the fluted(or corrugated) sheet.

Also, typically, the media can contain a resin. During the corrugationprocess, the media can be heated to above the glass transition point ofthe resin. When the resin then cools, it will help to maintain thefluted shapes.

The media of the fluted sheet 3, facing sheet 4 or both, can be providedwith a fine fiber material on one or both sides thereof, for example inaccord with U.S. Pat. Nos. 6,955,775, 6,673,136, and 7,270,693,incorporated herein by reference. In general, fine fiber can be referredto as polymer fine fiber (microfiber and nanofiber) and can be providedon the media to improve filtration performance. As a result of thepresence of fine fiber on the media, it may be possible or desirable toprovide media having a reduced weight or thickness while obtainingdesired filtration properties. Accordingly, the presence of fine fiberon media can provide enhanced filtration properties, provide for the useof lighter media, or both. Fiber characterized as fine fiber can have adiameter of about 0.001 micron to about 10 microns, about 0.005 micronto about 5 microns, or about 0.01 micron to about 0.5 micron. Nanofiberrefers to a fiber having a diameter of less than 200 nanometer or 0.2micron. Microfiber can refer to fiber having a diameter larger than 0.2micron, but not larger than 10 microns. Exemplary materials that can beused to form the fine fibers include polyvinylidene chloride, polyvinylalcohol polymers and co-polymers comprising various nylons such as nylon6, nylon 4, 6, nylon 6, 6, nylon 6, 10, and co-polymers thereof,polyvinyl chloride, PVDC, polystyrene, polyacrylonitrile, PMMA, PVDF,polyamides, and mixtures thereof.

Still referring to FIG. 1, at 20 tack beads are shown positioned betweenthe fluted sheet 3 and facing sheet 4, securing the two together. Thetack beads 20 can be for example, discontinuous lines of adhesive. Thetack beads can also be points in which the media sheets are weldedtogether.

From the above, it will be apparent that the exemplary fluted sheet 3depicted is typically not secured continuously to the facing sheet,along the peaks where the two adjoin. Thus, air can flow betweenadjacent inlet flutes, and alternately between the adjacent outletflutes, without passage through the media. However, unfiltered air whichhas entered a flute through the inlet flow face cannot exit from a flutethrough the outlet flow face without passing through at least one sheetof media, with filtering.

Attention is now directed to FIG. 2, in which a z-filter mediaconstruction 40 utilizing a fluted (in this instance regular, curved,wave pattern corrugated) sheet 43, and a non-corrugated flat, facingsheet 44, is depicted. The distance D1, between points 50 and 51,defines the extension of flat media 44 in region 52 underneath a givenflute 53. The points 50 and 51 are provided as the center point of theinternal peaks 46 and 48 of the fluted sheet 43. In addition, the point45 can be characterized as the center point of the external peak 49 ofthe fluted sheet 43. The distance D1 defines the period length orinterval of the media construction 40. The length D2 defines the arcuatemedia length for the flute 53, over the same distance D1, and is ofcourse larger than D1 due to the shape of the flute 53. For a typicalregular shaped media used in fluted filter applications according to theprior art, the ratio of the lengths D2 to D1 will be within a range of1.2-2.0, inclusive. An exemplary arrangement common for air filters hasa configuration in which D2 is about 1.25×D1 to about 1.35×D1. Suchmedia has, for example, been used commercially in Donaldson Powercore™Z-filter arrangements. Herein the ratio D2/D1 will sometimes becharacterized as the flute/flat ratio or media draw for the media.

The flute height J is the distance from the flat, facing sheet 44 to thehighest point of the fluted sheet 43. Alternatively stated, the fluteheight J is the difference in exterior elevation between alternatingpeaks 57 and 58 of the fluted sheet 43. The peak 57 can be referred toas the internal peak (the peak directed toward the facing sheet 44), andthe peak 58 can be referred to as the external peak (the peak directedaway from the facing sheet 44). Although the distances D1, D2, and J areapplied to the specific fluted media arrangement shown in FIG. 2, thesedistances can be applied to other configurations of fluted media whereD1 refers to the period length of a flute or the distance of flat mediaunderneath a given flute, D2 refers to the length of fluted media fromlower peak to lower peak, and J refers to the flute height.

Another measurement can be referred to as the cord length (CL). The cordlength refers to the straight line distance from the center point 50 ofthe peak 57 and the center point 45 of the peak 58. The thickness of themedia and the decision where to begin or end a particular distancemeasurement can affect the distance value if the media thickness affectsthe distance value. For example, the cord length (CL) can have adifferent value depending upon whether the distance is measured from thebottom of the internal peak to the bottom of the external peak orwhether it is measured from the bottom of the internal peak to the topof the external peak. This difference in distance is an example of howthe media thickness affects the distance measurement. In order tominimize the effect of the thickness of the media, the measurement forcord length is determined from a center point within the media. Therelationship between the cord length CL and the media length D2 can becharacterized as a media-cord percentage. The media-cord percentage canbe determined according to the following formula:

${{media}\text{-}{cord}\mspace{14mu}{percentage}} = \frac{{\frac{1}{2}D_{2}} - {{CL} \times 100}}{CL}$

In the corrugated cardboard industry, various standard flutes have beendefined. These include, for example, the standard E flute, standard Xflute, standard B flute, standard C flute, and standard A flute. FIG. 3,attached, in combination with Table 1 below provides definitions ofthese flutes.

Donaldson Company, Inc., (DCI) the assignee of the present disclosure,has used variations of the standard A and standard B flutes, in avariety of z-filter arrangements. The DCI standard B flute can have amedia-cord percentage of about 3.6%. The DCI standard A flute can have amedia-cord percentage of about 6.3. Various flutes are also defined inTable 1 and FIG. 3. FIG. 2 shows a z-filter media construction 40utilizing the standard B flute as the fluted sheet 43.

TABLE 1 (Flute definitions for FIG. 3) DCI A Flute: Flute/flat = 1.52:1;The Radii (R) are as follows: R1000 = .0675 inch (1.715 mm); R1001 =.0581 inch (1.476 mm); R1002 = .0575 inch (1.461 mm); R1003 = .0681 inch(1.730 mm); DCI B Flute: Flute/flat = 1.32:1; The Radii (R) are asfollows: R1004 = .0600 inch (1.524 mm); R1005 = .0520 inch (1.321 mm);R1006 = .0500 inch (1.270 mm); R1007 = .0620 inch (1.575 mm); Std. EFlute: Flute/flat = 1.24:1; The Radii (R) are as follows: R1008 = .0200inch (.508 mm); R1009 = .0300 inch (.762 mm); R1010 = .0100 inch (.254mm); R1011 = .0400 inch (1.016 mm); Std. X Flute: Flute/flat = 1.29:1;The Radii (R) are as follows: R1012 = .0250 inch (.635 mm); R1013 =.0150 inch (.381 mm); Std. B Flute: Flute/flat = 1.29:1; The Radii (R)are as follows: R1014 = .0410 inch (1.041 mm); R1015 = .0310 inch (.7874mm); R1016 = .0310 inch (.7874 mm); Std. C Flute: Flute/flat = 1.46:1;The Radii (R) are as follows: R1017 = .0720 inch (1.829 mm); R1018 =.0620 inch (1.575 mm); Std. A Flute: Flute/flat = 1.53:1; The Radii (R)are as follows: R1019 = .0720 inch (1.829 mm); R1020 = .0620 inch (1.575mm).

In general, standard flute configurations from the corrugated boxindustry have been used to define corrugation shapes or approximatecorrugation shapes for corrugated media. Improved performance offiltration media can be achieved by providing a flute configuration orstructure that enhances filtration. In the corrugated box boardindustry, the size of the flutes or the geometry of the corrugation wasselected to provide a structure suited for handling a load. The flutegeometry in the corrugated box industry developed the standard A fluteor B flute configuration. While such flute configurations can bedesirable for handling a load, filtration performance can be enhanced byaltering the flute geometry. Techniques for improving filtrationperformance include selecting geometries and configurations that improvefiltration performance in general, and that improve filtrationperformance under selected filtration conditions. Exemplary flutegeometries and configurations that can be altered to improve filtrationperformance include flute masking, flute shape, flute width heightratio, and flute asymmetry. In view of the wide selection of flutegeometries and configurations, the filter element can be configured withdesired filter element geometries and configurations in view of thevarious flute geometries and configurations to improve filtrationperformance.

Masking

In the context of z-media, masking refers to the area of proximitybetween the fluted sheet and the facing sheet where there is a lack ofsubstantial pressure difference resulting in a lack of useful filtrationmedia when the filtration media is in use. In general, masked media isnot useful for significantly enhancing the filtration performance offiltration media. Accordingly, it is desirable to reduce masking tothereby increase the amount of filtration media available for filtrationand thereby increase the capacity of the filtration media, increase thethroughput of the filtration media, decrease the pressure drop of thefiltration media, or some or all of these.

In the case of a fluted sheet arranged in a pattern with broad radii atthe peaks as shown in FIG. 2, there exists a relatively large area offiltration media proximate the contact area of the fluted sheet and thefacing sheets that is generally not available for filtration. Maskingcan be reduced by decreasing the radii of the peak or contact pointbetween the fluted sheet and the facing sheet (e.g., providing sharpercontact points). Masking generally takes into account the deflection ofthe media when it is under pressure (e.g., during air filtration). Arelatively large radius may result in more of the fluted media beingdeflected toward the facing sheet and thereby increasing masking. Byproviding a sharper peak or contact point (e.g., a smaller radius),masking can be reduced.

Attempts have been made to reduce the radii of contact between thefluted sheet and the facing sheet. For example, see U.S. Pat. No.6,953,124 to Winter et al. An example of reducing the radii is shown inFIG. 4 a where the fluted sheet 70 contacts the facing sheets 72 and 73at relatively sharp peaks or contact points 74 and 75 in the flutedsheet 70. A curved wave pattern such as the curved wave pattern shown inFIG. 1 generally provides a fluted sheet having a radius at the peaks ofat least 0.25 mm and typically not more than 3 mm. A relatively sharppeak or contact point can be characterized as a peak having a radius ofless than 0.25 mm. Preferably, the relatively peak point can be providedhaving a radius of less than about 0.20 mm. In addition, masking can bereduced by providing a peak having a radius of less than about 0.15 mm,and preferably less than about 0.10 mm. The peak can be provided havingno radius or essentially a radius of about 0 mm. Exemplary techniquesfor providing fluted media exhibiting relatively sharp peaks or contactpoints includes coining, bending, folding, or creasing the fluted mediain a manner sufficient to provide a relatively sharp edge. It should beunderstood that the ability to provide a sharp edge depends on a numberof factors including the composition of the media itself and theprocessing equipment used for providing coining, bending, folding, orcreasing. In general, the ability to provide a relatively sharp contactpoint depends on the weight of the media and whether the media containsfibers that resist tearing or cutting. In general, it is desirable tonot cut the filtration media during coining, bending, folding, orcreasing.

While it is desirable to reduce the radius of the peak (internal peak orexternal peak) to reduce masking, it is not necessary that all of thepeaks have a reduced radius to decrease masking. Depending on the designof the media, it may be sufficient to provide the external peaks with areduced radius or to provide the internal peaks with a reduced radius,or to provide both the external peaks and the internal peaks with areduced radius in order to decrease masking

Increasing the Surface Area of Media

Filtration performance can be enhanced by increasing the amount offiltration media available for filtration. Reducing masking can beconsidered a technique for increasing the surface area of mediaavailable for filtration. Now referring to FIG. 4 a, the fluted sheet 70can be considered to provide flutes having a cross-section resembling anequilateral triangle. Because the media is flexible, it is expected thatwhen the media is subjected to pressure such as during air filtration,the fluted sheet 70 may deflect. In addition, the fluted sheet 43 inFIG. 2 can be considered to have flutes resembling a triangular shape.In general, fluted media where the flutes resemble equilateral trianglesgenerally provides the least amount of media available for filtrationcompared with other flute designs where the period length or interval D1is increased or decreased, or the flute height J is increased ordeceased, relative to the other.

Now referring to FIGS. 4 b and 4 c, FIG. 4 b refers to media where thefluted sheet 80 extends between the facing sheets 82 and 83. FIG. 4 cshows media where the fluted sheet 90 extends between the facing sheets92 and 93. The fluted sheet 80 is shown having a longer flute periodthan the fluted sheet 70 in FIG. 4 a. Accordingly, the fluted sheet 80is provided having a relatively long period D1 relative to the fluteheight J compared with the media configuration shown in FIG. 4 a. Nowreferring to FIG. 4 c, the fluted sheet 90 is shown having a shorterflute period than the fluted sheet 70 in FIG. 4 a. The fluted sheet 90is shown having a relatively large flute height J relative to the periodD1 compared with the media configuration shown in FIG. 4 a.

The configuration of the fluted media can be characterized by the flutewidth height ratio. The flute width height ratio is the ratio of theflute period length D1 to the flute height J. The flute width heightratio can be expressed by the following formula:

${{flute}\mspace{14mu}{width}\mspace{14mu}{height}\mspace{14mu}{ratio}} = \frac{D\; 1}{J}$Measured distances such as flute period length D1 and the flute height Jcan be characterized as average values for the filtration media alongthe flute length within 20% of each flute end. Accordingly, thedistances can be measured away from the ends of the flutes. It istypically the ends of the flutes that have a sealant or closure. Theflute width height ratio calculated at a flute closure would notnecessarily represent the flute width height ratio of the flute wherethe filtration is taking place. Accordingly, the measure of flute widthheight ratio can be provided as an average value over the flute lengthwith the exception of the last 20% of the flute length near the ends ofthe flutes to remove the effects of flute closure when the flutes areclosed near the ends. For “regular” media, it is expected that the fluteperiod length D1 and the flute height J will be relatively constantalong the flute length. By relatively constant, it is meant that theflute width height ratio can vary within about 10% over the length ofthe flute excluding the 20% length at each end when flute closuredesigns may effect the width height ratio. In addition, in the case of anon-regular media, such as, media having tapered flutes, the flute widthheight ratio can vary or remain about the same over the length of theflute. By adjusting the flute shape away from a theoretical equilateraltriangle shape, the amount of media available for filtration can beincreased. Accordingly, flutes having a flute width height ratio of atleast about 2.2, at least about 2.5, at least about 2.7, or at leastabout 3.0 can provide an increased surface area of media available forfiltration. In addition, providing a flute design having a width heightratio of less than about 0.45, less than about 0.40, less than about0.37, or less than about 0.33 can provide increased media area availablefor filtration.Flute Shape

The performance of the filtration media can be enhanced by modifying theflute shape. Providing a flute shape that increases the amount offiltration media available for filtration can increase performance. Onetechnique for increasing the amount of filtration media available forfiltration is by creating a ridge between adjacent peaks. As discussedpreviously, adjacent peaks refers to an internal peak (facing toward thefacing sheet) and an external peak (facing away from the facing sheet).FIGS. 5 a-5 c show representative exemplary flute shapes for enhancingfiltration performance. The flute shape shown in FIG. 5 a can bereferred to as a “low contact” flute shape. The flute shapes shown inFIGS. 5 b and 5 c can be referred to as “zero strain” flute shapes. Ingeneral, the “low contact” name refers to the ability of the flute shapeto enhance the amount of fluted media sheet between the facing mediasheets while reducing the amount of contact (e.g., masking) between thefluted sheet and the facing sheet compared with standard A and B flutedmedia. The “zero strain” name refers to the ability of the flute shapeto provide a taper along a length of the flutes without inducing anundesired level of strain on the media. In general, an undesired levelof strain (or elongation) in the media can refer to an amount of strainthat causes a tear or rip in the media, or an amount of strain thatrequires the use of a special media that can withstand a higher level ofstrain. In general, media that can withstand a strain of greater thanabout 12% can typically be considered a special media, and can be moreexpensive than media that is equipped to handle strain up to about 12%.The zero strain fluted sheet can additionally provide for reducedcontact between the fluted sheet and the facing sheet.

Now referring to FIGS. 5 a-5 c, the media 110 includes fluted sheet 112between facing sheets 111 and 113, the media 120 includes fluted sheet122 between facing sheets 121 and 123, and the media 140 includes flutedsheet 142 between facing sheets 141 and 143. The combination of thefluted sheet 112 and the facing sheet 113 can be referred to as a singlefacer media 117, the combination of the fluted sheet 122 and the facingsheet 123 can be referred to as the single facer media 137, and thecombination of fluted sheet 142 and facing sheet 143 can be referred toas the single facer media 147. When the single facer media 117, 137, or147 is coiled or stacked, the facing sheet 111, 121, or 141 can beprovided from another single facer media in the case of stacked media orfrom the same single facer media in the case of coiled media.

The media 110, 120, and 140 can be arranged to provide filter elementsfor cleaning a fluid such as air. The filter elements can be arranged ascoiled elements or stacked elements. Coiled elements generally include afluted media sheet and a facing media sheet that is wound to provide thecoiled construction. The coil construction can be provided having ashape that is characterized as round, obround, or racetrack. A stackedconstruction generally includes alternating layers of media comprisingfluted media sheet adhered to facing media sheet. The media 110, 120,and 140 shown in FIGS. 5 a-5 c are sectional views taken across themedia to show the cross-sectional shape of the fluted sheet for thedescribed shapes. It should be understood that the cross-sectional shapecan be provided extending along a length of the flute. Furthermore, theflutes can be closed or sealed so that the media functions as z-media.The closure or seal can be provided, if desired, as an adhesive orsealant material.

In FIG. 5 a, the distance D1 is measured from the center point of theinternal peak 114 to the center point of the external peak 116. Thefluted media 110 is shown having two ridges 118 for each period lengthD1, or along the media length D2. The ridges 118 are provided extendingalong at least a portion of the length of the flute. In general, eachridge 118 can be characterized as a general area where a relativelyflatter portion of the fluted media 118 a joins a relatively steeperportion of the fluted media 118 b. A ridge (e.g., a non-peak ridge) canbe considered a line of intersection between differently sloped mediaportions. A ridge can be formed as a result of deformation of the mediaat that location. The media can be deformed at the ridge as a result ofapplying pressure to the media. Techniques for forming the ridge includecoining, creasing, bending, and folding. Preferably, the ridge can beprovided as a result of coining during a corrugation process where thecorrugation rolls apply pressure to the media to form the ridge. Anexemplary technique for forming the fluted sheet and the single spacermedia is described in U.S. Application Ser. No. 61/025,999 that wasfiled with the United States Patent and Trademark Office on Feb. 4,2008. The entire disclosure of U.S. Application Ser. No. 61/025,999 isincorporated herein by reference.

For the exemplary fluted sheet 112, the relatively flatter portion ofthe fluted media 118 a can be seen in FIG. 5 a as the portion of thefluted media extending between the external peak 115 and the ridge 118.The average angle of the relatively flatter portion of the fluted media118 a from the external peak 115 to the ridge 118 can be characterizedas less than 45°, and can be provided as less than about 30° relative tothe facing sheet 113. The relatively steeper portion of the fluted media118 b can be characterized as that portion of the media extending fromthe internal peak 116 to the ridge 118. In general, the angle of therelatively steeper portion of the fluted media 118 b, as characterizedas extending between the internal peak 116 and the ridge 118 can begreater than 45° and can be greater than about 60° relative to thefacing sheet 113. It is the difference in angle between the relativelyflatter portion of the fluted media 118 a and the relatively steeperportion of the fluted media 118 b that can characterize the presence ofthe ridge 118. It should be understood that the angle of the relativelyflatter portion of the fluted media 118 a and angle of the relativelysteeper portion of the fluted media 118 b can be determined as theaverage angle between the points that form the end points of the sectionof the media, and the angle is measured from the facing sheet.

The ridge 118 can be provided as a result of coining, creasing, bending,or folding along a length of the fluted sheet 112 during the formationof the fluted media 12. It may be desirable, but it is not necessary,during the step of forming the fluted media 112 to take the steps to setthe ridge 118. For example, the ridge 118 can be set by heat treatmentor moisture treatment or a combination thereof. In addition, the ridge118 can exist as a result of coining, creasing, bending, or folding toform the ridge without an additional step of setting the ridge.Furthermore, the characterization of a ridge 118 is not to be confusedwith the fluted sheet external peaks 115 or 119 and the fluted sheetinternal peaks 116 or 114. The characterization of a generally flatterportion 118 a and a generally steeper portion 118 b is intended as a wayto characterize the presence of a ridge. In general, it is expected thatthe flatter portion 118 a and the steeper portion 118 b will exhibit acurve. That is, it is expected that the flatter portion 118 a and thesteeper portion 118 b will not be completely planar, particularly asfluids such as air flows through the media during filtration.Nevertheless, the angle of the media can be measured from the ridge tothe corresponding, adjacent peak to provide the average angle of thatportion of the media.

The shape of the media depicted in FIG. 5 a can be referred to as a lowcontact shape. In general, the low contact shape refers to therelatively low area of contact between the fluted sheet 112 and thefacing sheet 111. The presence of the ridge 118 helps provide forreduced masking at the peaks 115 and 119. The ridge 118 exists as aresult of deforming the fluted sheet 112 and, as a result, reduces theinternal stress on the media at the peaks 115 and 119. Without thepresence of the ridge 118, there would likely exist a level of internaltension in the fluted sheet 112 that would cause the fluted sheet 112 tocreate a greater radius at the peaks 115 and 119, and thereby increasemasking. As a result, the presence of the ridge 118 helps increase theamount of media present between adjacent peaks (e.g., peaks 115 and 114)and helps decrease the radius of a peak (e.g., peak 115) as a result ofrelieving, to a certain extent, the tension within the fluted sheet 112that would cause it to expand or flatten out at the peaks in the absenceof the ridge.

The presence of a ridge 118 can be detected by visual observation. FIG.6 shows a photograph of an end view of a filter element wherein thefluted media can be characterized as having the low contact shape. Whilethe presence of the low contact shape may not be particularly apparentfrom viewing the end of the fluted media, one can cut into the filterelement and see the presence of a ridge extending along a length of aflute. Furthermore, the presence of a ridge can be confirmed by atechnique demonstrated by the photograph of FIG. 7 where the filterelement is loaded with dust, and the fluted sheet can be peeled awayfrom the facing sheet to reveal a cake of dust having a ridgecorresponding to the ridge on the fluted media. In general, the ridge ona cake of dust reflects a portion of the dust surface having an averageangle intersecting another portion of the dust surface having adifferent average angle. The intersection of the two portions of thedust surface cake forms a ridge. The dust that can be used to load themedia to fill the flutes to provide a cake of dust within the flutes canbe characterized as ISO Fine test dust.

Now referring to FIG. 5 a, the fluted sheet 112 includes two ridges 118over the distance D2 where the distance D2 refers to the length of thefluted sheet 112 from the center point of the peak 114 to the centerpoint of the peak 116, and wherein the ridges are not the peaks 114,115, 116, or 119. Although the peaks 114 and 116 can be referred to asinternal peaks, and the peaks 115 and 119 can be referred to as theexternal peak, the peaks can additionally be characterized as the facingsheet peaks. In general, it is believed that the media will be arrangedin different configurations such as wound or stacked and that the fluteswill be arranged spacially so that the characterizations of internal andexternal can be disregarded in favor of the use of the characterizationof the peak as a facing sheet peak. The use of the terms internal andexternal is convenient for describing the flute as it is shown in thefigures. Although the fluted sheet 112 can be provided having two ridges118 along each length D2, the fluted sheet 112 can be provided having asingle ridge along each period length D2, if desired, and can beprovided having a configuration where some of the periods exhibit atleast one ridge, some periods exhibit two ridges, and some periodsexhibit no ridge, or any combination thereof. The fluted sheet can becharacterized as having a repeating pattern of flutes having at leastone ridge in the repeating pattern. A repeating pattern of flutes meansthat the wave pattern exhibits a pattern that repeats over the directiontransverse to the flute direction. The repeating pattern may be everyadjacent peak, every other adjacent peak, every third adjacent peak,etc., or some variation that can be perceived as a pattern over themedia.

The characterization of the presence of a ridge should be understood tomean that the ridge is present along a length of the flute. In general,the ridge can be provided along the flute for a length sufficient toprovide the resulting media with the desired performance. While theridge may extend the entire length of the flute, it is possible that theridge will not extend the entire length of the flute as a result of, forexample, influences at the ends of the flute. Exemplary influencesinclude flute closure (e.g., darting) and the presence of plugs at theends of flutes. Preferably, the ridge extends at least 20% of the flutelength. By way of example, the ridge can extend at least 30% of theflute length, at least 40% of the flute length, at least 50% of theflute length, at least 60% of the flute length, or at least 80% of theflute length. The ends of the flutes may be closed in some manner andthat as a result of the closure, one may or may not be able to detectthe presence of a ridge when viewing the media pack from a face.Accordingly, the characterization of the presence of a ridge asextending along a length of the flute does not mean that the ridge mustextend along the entire length of the flute. Furthermore, the ridge maynot be detected at the ends of the flute. Attention is directed to thephotograph of FIG. 6 where it may be somewhat difficult to detect thepresence of a ridge at the end of fluted media although the presence ofthe ridge can be detected within the media at a distance from the end ofthe flute.

Now referring to FIG. 5 b, the fluted media 120 includes a fluted sheet122 provided between facing sheets 121 and 123. The fluted sheet 122includes at least two ridges 128 and 129 between the internal peak 124and the external peak 125. Along the length D2, the media 122 includesfour ridges 128 and 129. A single period length of media can includefour ridges. It should be understood that the ridges 128 and 129 are notthe peaks 124, 125, or 126 that can be referred to as the facing sheetpeaks. The media 122 can be provided so that between adjacent peaks(e.g., peaks 125 and 126) there are two ridges 128 and 129. In addition,the fluted sheet 122 can be provided so that between other adjacentpeaks, there is one ridge or no ridge. There is no requirement thatbetween each adjacent peak there are two ridges. There can be an absenceof ridges between peaks if it is desirable to have the presence ofridges alternate or provided at predetermined intervals between adjacentpeaks.

The ridge 128 can be characterized as the area where a relativelyflatter portion of the fluted media 128 a joins a relatively steeperportion of the fluted media 128 b. In general, the relatively flatterportion of the fluted media 128 a can be characterized as having anangle of less than 45° and preferably less than about 30° wherein theangle is measured for the media between the ridge 128 and the ridge 129and relative to the facing sheet 123. The relatively steeper portion ofthe fluted media 128 b can be characterized as having an angle ofgreater than 45° and preferably greater than about 60° wherein the angleis measured for the media from the peak 126 to the ridge 128 andrelative to the facing sheet 123. The ridge 129 can be provided as aresult of the intersection of the relatively flatter portion of thefluted media 129 a and the relatively steeper portion of the flutedmedia 129 b. In general, the relatively flatter portion of the flutedmedia 129 a corresponds to the angle of the portion of the mediaextending from the ridge 128 to the ridge 129 and relative to the facingsheet 123. In general, the relatively flatter portion of the flutedmedia 129 a can be characterized as having a slope of less than 45°, andpreferably less than about 30°. The relatively steeper portion of thefluted media 129 b can be characterized as that portion of the flutedmedia extending between the ridge 129 and the peak 125 and can becharacterized as having an angle measure for the media between the ridge129 and the peak 125 and relative to the facing sheet 123. In general,the relatively steeper portion of the fluted media 129 b can becharacterized as having an angle of greater than 45° and preferablygreater than about 60°.

Now referring to FIG. 5 c, the fluted media 140 includes a fluted sheet142 provided between facing sheets 141 and 143. The fluted sheet 142includes at least two ridges 148 and 149 between the internal peak 144and the external peak 145. Along the length D2, the media 140 includesfour ridges 148 and 149. A single period length of media can includefour ridges. It should be understood that the ridges 148 and 149 are notthe peaks 144 and 145. The media 140 can be provided so that betweenadjacent peaks (e.g., peaks 144 and 145) there are two ridges 148 and149. In addition, the fluted sheet 140 can be provided so that betweenother adjacent peaks, there is one ridge, two ridges, or no ridge. Thereis no requirement that between each adjacent peak there are two ridges.There can be an absence of ridges between peaks if it is desirable tohave the presence of ridges alternate or provided at predeterminedintervals between adjacent peaks. In general, a pattern of flutes can beprovided where the pattern of flutes repeats and includes the presenceof ridges between adjacent peaks.

The ridges 148 and 149 can be characterized as the areas where arelatively flatter portion of the fluted sheet joins a relativelysteeper portion of the fluted sheet. In the case of the ridge 148, arelatively flatter portion of the fluted sheet 148 a joins a relativelysteeper portion of the fluted sheet 148 b. In the case of the ridge 149,a relatively flatter portion of the fluted sheet 149 a joins arelatively steeper portion of the fluted sheet 149 b. The relativelysteeper portion of the fluted media can be characterized as having anangle of greater than 45° and preferably greater than about 60° whenmeasured for that portion of the media relative to the facing sheet 143.The relatively flatter portion can be characterized as having a slope ofless than 45° and preferably less than about 30° for that portion of themedia relative to the facing sheet 143.

The fluted sheet 142 can be considered more advantageous to preparerelative to the fluted sheet 122 because the wrap angle of the flutedsheet 142 can be less than the wrap angle for the fluted sheet 122. Ingeneral, the wrap angle refers to the sum of angles resulting in mediaturns during the step of fluting. In the case of the fluted media 142,the media is turned less during fluting compared with the fluted media122. As a result, by fluting to form the fluted sheet 142, the requiredtencile strength of the media is lower compared with the fluted sheet122.

The fluted sheets 112, 122, and 142 are shown as relatively symmetricalfrom peak to peak. That is, for the fluted sheets 112, 122, and 142, theflutes repeat having the same number of ridges between adjacent peaks.Adjacent peaks refer to the peaks next to each other along a length offluted media. For example, for the fluted sheet 112, peaks 114 and 115are considered adjacent peaks. A period of media, however, need not havethe same number of ridges between adjacent peaks, and the media can becharacterized as asymmetrical in this manner. That is, the media can beprepared having a ridge on one half of the period and not having a ridgeon the other half of the period.

By providing a single ridge or multiple ridges between adjacent peaks ofthe fluted media, the distance D2 can be increased relative to prior artmedia such as standard A and B flutes. As a result of the presence of aridge or a plurality of ridges, it is possible to provide filtrationmedia having more media available for filtration compared with, forexample, standard A flutes and B flutes. The previously describedmeasurement of media-cord percentage can be used to characterize theamount of media provided between adjacent peaks. The length D2 isdefined as the length of the fluted sheet 112, 122, and 142 for a periodof the fluted sheet 112, 122, and 142. In the case of the fluted sheet112, the distance D2 is the length of the fluted sheet from the lowerpeak 114 to the lower peak 116. This distance includes two ridges 118.In the case of the fluted sheet 122, the length D2 is the distance ofthe fluted sheet 122 from the lower peak 124 to the lower peak 126. Thisdistance includes at least four ridges 128 and 129. The existence ofincreased filtration media between adjacent peaks as a result ofproviding one or more ridge (or crease) between the adjacent peaks canbe characterized by the media-cord percentage. As discussed previously,standard B flutes and standard A flutes have a media-cord percentage ofabout 3.6% and about 6.3%, respectively. In general, low contact flutessuch as the flute design shown in FIG. 5 a can exhibit a media-cordpercentage of about 6.2% to about 8.2%. The flute designs shown in FIGS.5 b and 5 c can provide a media-cord percentage of about 7.0% to about16%.

The filtration media 120 and 140 in FIGS. 5 b and 5 c has an additionaladvantage of providing the ability to taper flutes along the length ofthe flute without creating a strain in the media. As a result of this,the flute shapes referred to in FIGS. 5 b and 5 c can be referred to asthe zero strain flute shapes. Now referring to FIGS. 8 and 9 a, thefluted sheet 122 is shown in a tapered configuration. In FIG. 9 a, thefluted sheet 122 is shown tapering from the configuration 122 a to theconfiguration 122 d. As a result of the taper, the fluted media includesthe configurations shown as 122 b and 122 c. As the fluted media tapersfrom 122 a to 122 d, the ridges 128 and the ridges 129 approach thelower peaks 126 and move away from the upper peaks 125. Accordingly, asthe fluted media 122 tapers from 122 a to 122 d, the cross sectionalsurface area between the fluted sheet 122 and the facing sheet 123decreases. Corresponding with this decrease in cross sectional surfacearea, the corresponding flutes formed by the fluted sheet 122 and afacing sheet contacting the upper peaks 125 experience an increase incross sectional surface area. It is additionally observed that as thetaper moves toward the end configurations shown at 122 a and 122 d, theridges tend to merge together or become less distinguishable from eachother. The configuration shown at 122 a tends to look more like the lowcontact shape. In addition, it is seen that as the fluted media tapersfrom 122 d to 122 a, the ridges 128 and the ridges 129 approach theupper peaks 125.

An advantage of using the filtration media 120 where the fluted sheet122 contains ridges 128 and ridges 129 is the ability to taper theflutes without creating excessive strain, and the ability to usefiltration media that need not exhibit a strain greater than 12%. Ingeneral, strain can be characterized by the following equation:

${strain} = {\frac{{D\; 2\mspace{14mu}\max} - {D\; 2\mspace{14mu}\min}}{D\; 2\mspace{14mu}\min} \times 100}$D2 min refers to the media distance where the media is relaxed orwithout strain, and D2 max refers to the media distance under strain ata point prior to tear. Filtration media that can withstand a strain ofup to about 12% is fairly commonly used in the filtration industry.Commonly used filtration media can be characterized as cellulosic based.In order to increase the strain that the media can withstand, syntheticfibers can be added to the media. As a result, it can be fairlyexpensive to use media that must withstand a strain greater than 12%.Accordingly, it is desirable to utilize a flute configuration thatprovides for tapering of the flute while minimizing the strain on themedia, and avoiding the necessity of using expensive media that cantolerate higher strains than 12%.

Now referring to FIG. 9 b, the fluted sheet 142 of FIG. 5 c is shown ina tapered configuration extending from locations 142 a to 142 b, andthen to 142 c. As the flute tapers to a smaller cross-sectional area(the area between the fluted sheet 142 and the facing sheet 143), theridges 148 and 149 move toward the peak 145. The reverse can also besaid. That is, as the cross-sectional area in the flute increases, theridges 148 and 149 move toward the peak 144.

The flute shapes exemplified in FIGS. 5 a-5 c can help provide forreducing the area of media that may become masked at the peaks comparedwith standard A and B fluted media. In addition, the shapes exemplifiedin FIGS. 5 a-5 c can help assist in increasing the amount of mediaavailable for filtration compared with standard A and B fluted media. InFIG. 5 a, viewing the fluted media 112 from the facing sheet 113, theridges 118 can be seen to provide the flute with a concave appearance.From the perspective of facing sheet 111, the ridges 118 can be seen toprovide the media extending between adjacent peaks with a convexappearance. Now referring to FIG. 5 b, the ridges 128 and 129 can beseen as providing both a concave and a convex appearance from eitherside of the fluted media 122 from peak to adjacent peak. It should beappreciated that the flutes are not actually concave or convex in viewof the presence of the ridges. Accordingly, the ridges provide atransition or discontinuity in the curve. Another way of characterizingthe presence of the ridge is by observing a discontinuity in the curveof the media wherein the discontinuity is not present in standard Aflutes and B flutes. Furthermore, it should be appreciated that theflute shapes depicted in FIGS. 5 a-5 c and 9 a-9 b are somewhatexaggerated. That is, after forming the fluted media, there will likelybe a degree of spring or memory in the media that causes it to bow outor curve. Furthermore, the application of fluid (e.g., air) through themedia may cause the media to deflect. As a result, the actual mediaprepared according to this description will not necessarily followprecisely along the drawings presented in FIGS. 5 a-5 c and 9 a-9 b.

The single facer media configurations shown in FIGS. 5 a-5 c can bereversed, if desired. For example, the single facer media 117 includesthe fluted sheet 112 and the facing sheet 113. If desired, the singlefacer media can be constructed so that it includes the fluted sheet 112and the facing sheet 111. Similarly, the single facer media shown inFIGS. 5 b and 5 c can be reversed, if desired. The characterization ofthe single facer media shown in FIGS. 5 a-5 c is provided for purposesof explaining the invention. One will understand that a single facermedia can be prepared by combining the fluted sheet with a facing sheetin a manner essentially opposite of that depicted in FIGS. 5 a-5 c. Thatis, after the step of fluting the fluted sheet, the fluted sheet can becombined with a facing sheet on either side of the fluted sheet.

Flute Volume Asymmetry

Flute volume asymmetry refers to a volumetric difference within a filterelement or filter cartridge between the upstream volume and thedownstream volume. The upstream volume refers to the volume of the mediathat receives the unfiltered air, and the downstream volume refers tothe volume of the media that receives the filtered air. Filter elementscan additionally be characterized as having a dirty air side and a cleanair side. In general, the dirty air side of filtration media refers tothe volume of media that receives the unfiltered air. The clean air siderefers to the volume of media that receives the filtered air that haspassed via filtering passage from the dirty air side. It can bedesirable to provide a media having a dirty air side or upstream volumethat is greater than the clean air side or downstream volume. It hasbeen observed that particulates in the air are deposited on the dirtyair side and, as a result, the capacity of the filtration media can bedetermined by the volume of the dirty air side. By providing volumeasymmetry, it is possible to increase the volume of the media availablefor receiving the dirty air side and thereby increase the capacity ofthe media pack.

Filtration media having the flute volume asymmetry exists when thedifference between the upstream volume and the downstream volume isgreater than 10%. Flute volume asymmetry can be expressed by thefollowing formula:

${{volume}\mspace{14mu}{asymmetry}} = \frac{{volume}_{upstream} - {{volume}_{downstream} \times 100}}{{volume}_{downstream}}$Preferably, media exhibiting volume asymmetry has volume asymmetry ofgreater than about 20%, and preferably about 40% to about 200%. Ingeneral, it may be desirable for the upstream volume to be greater thanthe downstream volume when it is desirable to maximize the life of themedia. Alternatively, there may be situations where it is desirable tominimize the upstream volume relative to the downstream volume. Forexample, in the case of a safety element, it may be desirable to providea safety element having a relatively low upstream volume so that themedia fills and prevents flow relatively quickly as an indicator thatfailure has occurred in an upstream filter element.

The volume asymmetry can be calculated by measuring the cross-sectionalsurface area of flutes from a photograph showing a sectional view of theflutes. If the flutes form a regular pattern, this measurement willyield the flute volume asymmetry. If the flutes are not regular (e.g.,tapered), then one can take several sections of the media and calculatethe flute volume asymmetry using accepted interpolation or extrapolationtechniques.

Flute design can be adjusted to provide a flute asymmetry that enhancesfiltration. In general, flute asymmetry refers to forming flutes havingnarrower peaks and widened arching troughs, or vice versa so that theupstream volume and downstream volume for the media are different. Anexample of a symmetric flute is provided in U.S. Patent ApplicationPublication No. US 2003/0121845 to Wagner et al. The disclosure of U.S.Patent Application Publication No. US 2003/0121845 is incorporatedherein by reference.

Now referring to FIGS. 10 a and 10 b, asymmetric flutes are shown by thefiltration media 150 and 160. The filtration media 150 shows a flutedsheet 152 between facing sheets 154 and 155. The fluted sheet 152 isconfigured to provide a greater volume between the fluted sheet 152 andthe facing sheet 154 than the volume defined by the fluted sheet 152 andthe facing sheet 155. As a result, the volume defined by the areabetween the fluted sheet 152 and the facing sheet 154 can be provided asthe upstream volume or as the dirty side volume when it is desired tomaximize the upstream volume or dirty side volume. The flute filtrationmedia 160 shows a fluted sheet 162 between facing sheets 164 and 165.The fluted sheet is configured to provide a greater volume between thefluted sheet 162 and the facing sheet 165. The area between the flutessheet 162 and the facing sheet 165 can be characterized, if desired, asthe upstream volume or the dirty side volume.

Darted Flutes

FIGS. 11-18 illustrate a technique for closing an end of a flute. Thetechnique can be referred to as darting and general techniques fordarting flutes are described in U.S. Patent Publication No. US2006/0163150 that published on Jul. 27, 2006. The entire disclosure ofU.S. Patent Publication No. US 2006/0163150 is incorporated herein byreference.

An exemplary darting technique that can be used to close flutes infiltration media according to the invention is shown in FIGS. 11-18.Although the darting technique provided in FIGS. 1-18 is shown in thecontext of prior art media, the darting technique can be applied tofluted media according to the present invention. For example, the flutedmedia shown in FIGS. 5 a-5 c can be darted according to the techniqueshown in FIGS. 11-18.

In general, darting can occur to provide closure after a facer bead 190is applied for securing a fluted sheet 204 to a facing sheet 206. Ingeneral, and as described in U.S. Patent Publication No. US2006/0163150, an indenting or darting wheel can be used to form theflutes 200 as shown in FIGS. 11-13, and a folder wheel can be used toform the flutes 200 as shown in FIGS. 14-18. As shown in FIGS. 11-13,the darting wheel deforms a portion 202 of the upper peak 204, byindenting or inverting it. By “inverting” and variants thereof, it ismeant that the upper peak 204 is indented or turned inward in adirection toward the facing sheet 206. FIG. 12 is a cross-sectional viewalong the mid-point of the inversion 210 created by the darting wheel.The inversion 210 is between a pair of peaks 212, 214 that are createdas a result of the darting process. The peaks 212, 214 together form aflute double peak 216. The peaks 212, 214 in the flute double peak 216have a height that is shorter than the height of the upper peak 204before inversion. FIG. 13 illustrates the cross-section of the flute 200at a portion of the flute 200 that did not engage the darting wheel, andthus was not deformed. As can be seen in FIG. 13, that portion of theflute 200 retains its original shape.

Attention is now directed to FIGS. 14-18. FIGS. 14-18 show sections ofthe darted section 198 after engagement with the folder wheel. FIG. 18,in particular, shows an end view of the darted section 198, incross-section. A fold arrangement 218 can be seen to form a darted flute220 with four creases 221 a, 221 b, 221 c, 221 d. The fold arrangement218 includes a flat first layer 222 that is secured to the facing sheet64. A second layer 224 is shown pressed against the flat first layer222. The second layer 224 is preferably formed from folding oppositeouter ends 226, 227 of the first layer 222.

Still referring to FIG. 18, two of the folds or creases 221 a, 221 bwill generally be referred to herein as “upper, inwardly directed” foldsor creases. The term “upper” in this context is meant to indicate thatthe creases lie on an upper portion of the entire fold 220, when thefold 220 is viewed in the orientation of FIG. 11. The term “inwardlydirected” is meant to refer to the fact that the fold line or creaseline of each crease 221 a, 221 b, is directed toward the other.

In FIG. 18, creases 221 c, 221 d, will generally be referred to hereinas “lower, outwardly directed” creases. The term “lower” in this contextrefers to the fact that the creases 221 c, 221 d are not located on thetop as are creases 221 a, 221 b, in the orientation of FIG. 14. The term“outwardly directed” is meant to indicate that the fold lines of thecreases 221 c, 221 d are directed away from one another.

The terms “upper” and “lower” as used in this context are meantspecifically to refer to the fold 220, when viewed from the orientationof FIG. 18. That is, they are not meant to be otherwise indicative ofdirection when the fold 120 is oriented in an actual product for use.

Based upon these characterizations and review of FIG. 18, it can be seenthat a preferred regular fold arrangement 218 according to FIG. 18 inthis disclosure is one which includes at least two “upper, inwardlydirected, creases.” These inwardly directed creases are unique and helpprovide an overall arrangement at which the folding does not cause asignificant encroachment on adjacent flutes. These two creases result inpart from folding tips 212, 214, FIG. 18, toward one another.

A third layer 228 can also be seen pressed against the second layer 224.The third layer 228 is formed by folding from opposite inner ends 230,231 of the third layer 228. In certain preferred implementations, thefacing sheet 206 will be secured to the fluted sheet 196 along the edgeopposite from the fold arrangement 218.

Another way of viewing the fold arrangement 218 is in reference to thegeometry of alternating peaks 204 and troughs 205 of the corrugatedsheet 196. The first layer 222 includes the inverted peak 210. Thesecond layer 224 corresponds to the double peak 216 that is foldedtoward, and in preferred arrangements, folded against the inverted peak210. It should be noted that the inverted peak 210 and the double peak216, corresponding to the second layer 224, is outside of the troughs205 on opposite sides of the ridge 204. In the example shown, there isalso the third layer 228, which extends from folded over ends 230, 231of the double peak 216.

FIGS. 15-17 show the shape of the flute 200 at different sections. FIG.17 shows an undeformed section of the flute 200. The inversion 210 canbe seen in FIGS. 15 and 16 extending along from where it engages thefacing sheet 206 (FIG. 18) to a point where it no longer exists (FIG.17). In FIGS. 15 and 16, the inversion 210 is spaced at differentlengths from the facing sheet 206.

A process used to provide a dart according to FIGS. 1-18 can be referredto as “center indenting,” “center inverting,” “center darting” or“center deformation.” By the term “center” in this context, again, it ismeant that the indentation or inversion occurred at an apex or center ofthe associated upper peak 80, engaged by the indenting or darting wheel.A deformation or indent will typically be considered herein to be acenter indent, as long as it occurs within 3 mm of the center of aridge. In the context of darting, the term “crease,” “fold,” or “foldline” are meant to indicate an edge formed by folding the media back onor over itself, with or without sealant or adhesive between portions ofthe media.

While the closure technique described in the context of FIGS. 11-18 canresult in a flute closure as shown in FIG. 18, it is possible thatduring darting, as a result of the flexibility of the media and thespeed at which the media is moving, the step of indenting may not occurprecisely at the apex or peak of the corrugated sheet 196. As a result,folding of the tips 112 and 114 may not be as symmetrical as shown. Infact, one of the tips 212 and 214 may become somewhat flattened whilethe other tip is folded. Furthermore, in certain flute designs, it maybe desirable to skip the indenting step. For example, the flute mighthave a height (J) that is sufficiently small so that the flute can bepressed closed to provide a repeating fold pattern without requiring astep of indenting the flute tip.

Plug Length and Flute Height

Z-media is sometimes characterized as having flutes extending from aninlet face to an outlet face and wherein a first portion of the flutescan be characterized as inlet flutes and a second portion of the flutescan be characterized as outlet flutes. The inlet flutes can be providedwith a plug or seal near the outlet face, and the outlet flutes can beprovided with a plug or seal near or adjacent the inlet face. Of course,alternatives of this arrangement are available. For example, the sealsor plugs need not be provided at or adjacent the inlet face or outletface. The seals or plugs can be provided away from the inlet face or theoutlet face, as desired. In the case of hot melt adhesive being used asa seal or plug, it is often found that the plug has a length of at leastabout 12 mm. The applicants have found that by reducing the plug length,it is possible to increase desirable characteristics of the filtrationmedia including capacity, lower initial pressure drop, reduced amount ofmedia, or combinations thereof. It can be desirable to provide a pluglength that is less than about 10 mm, preferably less than about 8 mm,and even more preferably less than about 6 mm.

The flute height (J) can be adjusted as desired depending uponfiltration conditions. In the case where a filter element utilizing themedia according to the present invention is used as a substitute for aconventional filter element that utilizes, for example, a standard Bflute, the height J can be about 0.075 inch to about 0.150 inch. In thecase where a filter element utilizing the media according to the presentinvention is used as a substitute for a conventional filter element thatutilizes, for example, a standard A flute, the height J can be about0.15 inch to about 0.25 inch.

Filter Elements

Now referring to FIGS. 19-28, filter elements are described that includean air filtration media pack. The air filtration media pack can includethe single facer media as described herein.

The air filtration media pack can be provided as part of a filterelement containing a radial seal as described in, for example, U.S. Pat.No. 6,350,291, U.S. Patent Application No. US 2005/0166561, andInternational Publication No. WO 2007/056589, the disclosures of whichare incorporated herein by reference. For example, referring to FIG. 19,the filter element 300 includes air filtration media pack 301 that canbe provided as a wound media pack 302 of single facer media, and caninclude a first face 304 and a second face 306. A frame 308 can beprovided on a first end of the media pack 310, and can extend beyond thefirst face 304. Furthermore, the frame 308 can include a step orreduction in circumference 312 and a support 314 that extends beyond thefirst face 304. A seal member 316 can be provided on the support 314.When the filter element 301 is introduced within the housing 320, theseal member 316 engages the housing sealing surface 322 to provide aseal so that unfiltered air does not bypass the air filtration mediapack 300. The seal member 316 can be characterized as a radial sealbecause the seal member 316 includes a seal surface 317 that engages thehousing sealing surface 322 in a radial direction to provide sealing. Inaddition, the frame 308 can include a media pack cross brace or supportstructure 324 that helps support the frame 308 and helps reducetelescoping of the air filtration media pack 300. An access cover 324can be provided for enclosing the filter element 300 within the housing320.

The air filtration media pack can be provided as part of a filterelement having a variation on the radial seal configuration. As shown inFIG. 20, the seal 330 can be relied upon for holding the frame 332 tothe media pack 334. As shown in FIG. 19, the frame 308 can be adhesivelyattached to the media pack 301. As shown in FIG. 20, the frame 332 canbe provided adjacent to the first face 336 and the seal 330 can beprovided so that it holds the support 332 onto the media pack 334without the use of additional adhesive. The seal 330 can becharacterized as an overmold seal in that it expands along both sides ofthe seal support 338 and onto the outer surface of the media pack 334 atthe first end 340.

The air filtration media pack can be provided as part of a filterelement according to U.S. Pat. No. 6,235,195, the entire disclosure ofwhich is incorporated herein by reference. Now referring to FIG. 21, thefilter element 350 includes a wound media pack 352 having an oblong orracetrack shape, and an axial pinch seal 354 attached to the end andcircumscribing the exterior of the media pack. The axial pinch seal 354is shown provided between the first face 356 and the second face 358 ofthe media pack. The axial pinch seal 354 includes a base portion 360 anda flange portion 362. The base portion 362 can be provided for attachingto the media pack. The flange portion 362 can be pinched between twosurfaces to create a seal. One of the surfaces can be a surface of thehousing that contains the filter element 350. In addition, the otherstructure that pinches the flange 362 can be an access cover or anotherstructure provided within the housing that helps maintain the seal sothat unfiltered air passes through the media pack without bypassing themedia pack. The filter element 350 can include a handle 364 extendingaxially from the first face 356. If desired, the handle can be providedextending axially from the second face 358. The handle 364 allows one topull or remove the filter element 350 from the housing.

Now referring to FIGS. 22-24, a filter element is shown at referencenumber 400. The filter element 400 includes a wound media pack 402, ahandle arrangement 404, and a seal arrangement 406. Details of thisfilter element construction can be found in U.S. Pat. No. 6,348,084, theentire disclosure of which is incorporated herein by reference. Thepreviously described single facer media can be used to prepare thefilter element 400.

The handle arrangement 404 includes a center board 408, handles 410, anda hook construction 412. The single facer media can be wound around thecenter board 408 so that the handles 410 extend axially from a firstface 414 of the media pack 402. The hook arrangement 412 can extend fromthe second face 416 of the media pack 402. The handles 410 allow anoperator to remove the filter element 400 from a housing. The hookconstruction 412 provides for attachment to a cross brace or supportstructure 420. The hook construction 412 includes hook members 422 and424 that engage the cross brace or support structure 420. The crossbrace or support structure 420 can be provided as part of a seal supportstructure 430 that extends from the second face 416 and includes a sealsupport member 432. A seal 434 can be provided on the seal supportmember to provide a seal between the filter element 400 and a housing.The seal 434 can be characterized as a radial seal when the seal isintended to provide sealing as a result of contact of a radially facingseal surface 436 and a housing seal surface.

The air filtration media pack can be provided as part of a gas turbinesystem as shown in U.S. Pat. No. 6,348,085, the entire disclosure ofwhich is incorporated herein by reference. An exemplary gas turbinefiltration element is shown at reference number 450 in FIG. 25. Thefilter element 450 can include a primary filter element 452 and asecondary filter element 454. The secondary filter element 454 can bereferred to as a safety filter element. The main filter element 452 canbe provided as an air filtration media pack as previously described inthis application. The air filtration media pack can be provided as aresult of winding a single facer media or as a result of stacking asingle facer media. The primary filter element 452 and the secondaryfilter element 454 can be secured within a sleeve member 460. The sleevemember 460 can include a flange 462 that includes a seal 464. Wheninstalled, the element 450 can be provided so that the flange 462 andseal 464 are provided adjacent a support 466 and held in place by aclamp 200 so that the seal 464 provides a sufficient seal so thatunfiltered air does not bypass the filter element 450.

Another filter element that can utilize the air filtration media pack isdescribed in U.S. Pat. No. 6,610,126, the entire disclosure of which isincorporated herein by reference. Now referring to FIG. 26, the filterelement 500 includes an air filtration media pack 502, a radial sealarrangement 504, and a dust seal or secondary seal arrangement 506. Thefilter element 500 can be provided within an air cleaner housing 510 andcan include, downstream of the filter element 500, a safety or secondaryfilter element 512. Furthermore, an access cover 514 can be provided forenclosing the housing 510. The housing 510 and the access cover 514 canpinch the dust seal 506 so that the dust seal 506 can be characterizedas a pinch seal.

The air filtration media pack can be provided as a stacked media packarrangement according to International Publication No. WO 2006/076479and International Publication No. WO 2006/076456, the disclosures ofwhich are incorporated herein by reference. Now referring to FIG. 27, afilter element is shown at reference number 600 that includes a stacked,blocked, media pack 602. The blocked stacked media pack 602 can becharacterized as a rectangular or right (normal) parallelogram mediapack. To seal the opposite ends of the media pack 602 are positionedside panels 604 and 606. The side panels 604 and 606 seal the lead endand tail end of each stacked, single facer media. The media pack 602 hasopposite flow faces 610 and 612. It is pointed out that no flow pathbetween faces 610 and 612 is provided that does not also require the airto pass through media of the media pack 602 and thus to be filtered. Aperipheral, perimeter, housing seal ring 614 is positioned in the airfilter element 600. The particular seal ring 614 depicted is an axialpinch seal ring. If desired, a protective sheath or panel can beprovided over the media pack surfaces 626 and 622.

The air filtration media pack can be provided as a stacked media packarrangement according to International Publication No. WO 2007/133635,the entire disclosure of which is incorporated herein by reference. Nowreferring to FIG. 28, a filter element is shown at reference number 650.The filter element 650 includes a stacked z-filter media arrangement 652having a first, in this instance, inlet face 654, and an oppositesecond, in this instance, outlet face 656. In addition, the filterelement 650 includes an upper side 660, a lower side 662, and oppositeside end 664 and 666. The stacked z-filter media arrangement 652generally comprises one or more stacks of strips of single facer mediawhere each strip comprises a fluted sheet secured to a facing sheet. Thestrips can be provided in a slanted arrangement. The strips areorganized with flutes extending between the inlet face 654 and theoutlet face 656. The filter element 650 depicted comprises a stackedz-filter media pack arrangement comprising two stacked media packsections 670 and 672. A seal member 680 can be molded to the media pack.

It should be appreciated that, in view of exemplary FIGS. 19-28, thatthe air filtration media pack can be provided in various configurationsto form filter elements that can then be used in various housingarrangements to provide enhanced performance.

EXAMPLES

Filter elements having media containing various flute designs werecompared using filter media performance modeling software. The filterelements were not constructed and tested for this example. Instead, thedimensions of the filter elements and the filter element components, theproperties and characteristics of the filter elements and the filterelement components, the conditions of use, and the characteristics ofthe air being filtered were inputted into a computer program that modelsfilter media performance. The filter media performance modeling softwarewas validated based upon tests run on actual Donaldson Company filtermedia. The results of the computer software modeling are expected tohave an error within about 10%. For the purpose of evaluating differentfilter media design alternatives, it is believed that an error value ofwithin about 10% is sufficiently low that the modeling software can beused to evaluate various design options.

Tables 2-5 include a characterization of the filter element and thecomputer generated results. The tables identify the size of the elementevaluated using the filter media performance modeling software. Theelement size refers to the overall size of the element. In Tables 2, 4,and 5, the elements are stacked panel z-media elements having a size of8 inches×12 inches×5 inches. In Table 3, the element is a coiled z-mediaelement having a size of 17 inch diameter×12 inch depth.

TABLE 2 Initial % of Pressure Initial Flute Drop Pressure Element HeightPlug Media (inches Drop of Size Flute Type (J) Length Thickness waterBase Element (inches) Comments and Size (inches) (mm) (inches) gauge)Filter 1 8 × 12 × 5 Baseline Standard B 0.103 12.7 0.0109 1.88 100%  2 8× 12 × 5 Element 1 plus Standard B 0.103 12.7 0.0109 1.65 88% darting 38 × 12 × 5 Element 2 plus Standard B 0.103 5 0.0109 1.65 88% reducingplug length 4 8 × 12 × 5 Element 3 plus Low contact 0.103 5 0.0109 1.8397% low contact shape 5 8 × 12 × 5 Element 4 plus Low contact 0.103 50.0109 1.97 105%  low contact shape 6 8 × 12 × 5 Element 5 plus Lowcontact 0.103 5 0.009 1.73 92% media thickness SAE Fine Loading to 12Inches % of % H₂O Loading Element Volume Media % Area Flow Pressure ofBase Volume of Base Required of Base Rate Element Drop Filter (ft³)Filter (ft²) Filter (cfm) 1 606 100% 0.2777 100% 65.7 100% 636 2 618102% 0.2777 100% 65.7 100% 636 3 837 138% 0.2777 100% 65.7 100% 636 41256 207% 0.2777 100% 67.4 103% 636 5 1228 203% 0.2777 100% 68.1 104%636 6 1328 219% 0.2777 100% 69.6 106% 636

TABLE 3 Initial % of Pressure Initial Flute Drop Pressure Height PlugMedia (inches Drop of Element Size Flute Type (J) Length Thickness waterBase Element (inches) Comments and Size (inches) (mm) (inches) gauge)Filter 7 17 diameter × Baseline with Standard A 0.196 15 0.0109 1.53 66% 12 deep A 8 17 diameter × Baseline with Standard B 0.103 15 0.01092.32 100% 12 deep B 9 17 diameter × Element 8 plus Standard B 0.103 150.0109 2.06  89% 12 deep darting 10 17 diameter × Element 9 plusStandard B 0.103 5 0.0109 2.37 102% 12 deep reducing plugs 11 17diameter × Element 10 Low 0.08 5 0.0109 3.14 135% 12 deep plus lowcontact contact 12 17 diameter × Element 11 Low 0.08 5 0.009 2.77 119%12 deep plus thinner contact media SAE Fine Loading to 12 Inches % of %H₂O Loading Element Volume Media % Area Flow Pressure of Base Volume ofBase Required of Base Rate Element Drop Filter (ft³) Filter (ft²) Filter(cfm) 7 5285  64% 1.57 100% 229  61% 1600 8 8279 100% 1.57 100% 374 100%1600 9 8385 101% 1.57 100% 374 100% 1600 10 9265 112% 1.57 100% 374 100%1600 11 11585 140% 1.57 100% 446 119% 1600 12 12688 153% 1.57 100% 458122% 1600

TABLE 4 Initial % of Pressure Initial Flute Drop Pressure Height MediaPlug (inches Drop of Element Size Flute Type (J) Thickness Size waterBase Element (inches) Comments and Size (inches) (inches) (mm) gauge)Filter 13 8 × 12 × 5 Baseline Standard B 0.1039 0.0109 12.7 1.92 100% 148 × 12 × 5 Element 13 Standard B 0.1039 0.0109 12.7 1.832  90% plusdarting 15 8 × 12 × 5 Element 14 Standard B 0.1039 0.0109 5 1.835  91%plus shorter plugs 16 8 × 12 × 5 Element 15 Low contact 0.1039 0.0109 51.045 114% plus low contact 17 8 × 12 × 5 Element 16 Low contact 0.10390.009 5 1.918 100% plus thinner media SAE Fine Loading to 12 Inches % of% H₂O Loading Element Volume Media % Area Flow Pressure of Base Volumeof Base Required of Base Rate Element Drop Filter (ft³) Filter (ft²)Filter (cfm) 13 1040 100% 0.2778 100% 65.69 100% 400 14 1046 101% 0.2778100% 65.69 100% 400 15 1345 129% 0.2778 100% 65.69 100% 400 16 1974 190%0.2778 100% 65.69 100% 400 17 2112 203% 0.2778 100% 69.58 106% 400

TABLE 5 Initial % of Pressure Initial Flute Drop Pressure Height MediaPlug (inches Drop of Element Size Flute Type (J) Thickness Size waterBase Element (inches) Comments and Size (inches) (inches) (mm) gauge)Filter 23 8 × 12 × 5 Baseline Standard B 0.1039 0.0109 12.7 3.164 100% 24 8 × 12 × 5 Element 23 Standard B 0.1039 0.0109 12.7 2.731 86% plusdarting 25 8 × 12 × 5 Element 25 Standard B 0.1039 0.0109 5 2.732 86%plus shorter plugs 26 8 × 12 × 5 Element 25 Low contact 0.1039 0.0109 53.12 99% plus low contact 27 8 × 12 × 5 Element 26 Low contact 0.10390.009 5 2.739 87% plus thinner media SAE Fine Loading to 12 Inches % of% H₂O Loading Element Volume Media % Area Flow Pressure of Base Volumeof Base Required of Base Rate Element Drop Filter (ft³) Filter (ft²)Filter (cfm) 23 368 100% 0.2778 100% 65.69 100% 872 24 384 104% 0.2778100% 65.69 100% 872 25 536 146% 0.2778 100% 65.69 100% 872 26 756 205%0.2778 100% 65.69 100% 872 27 834 227% 0.2778 100% 65.69 100% 872

The above specification, examples and data provide a completedescription of the manufacture and use of the filtration media andfilter element of the invention. Since many embodiments of the inventioncan be made without departing from the spirit and scope of theinvention, the invention resides in the claims hereinafter appended.

1. An air filtration media pack comprising: (a) a plurality of layers ofsingle facer media wherein the layer of single facer media comprising afluted sheet, a facing sheet, and a plurality of flutes extendingbetween the fluted sheet and the facing sheet and having a flute lengthextending from a first face of the filtration media pack to a secondface of the filtration media pack; (b) a first portion of the pluralityof flutes being closed to unfiltered air flowing into the first portionof the plurality of flutes, and a second portion of the plurality offlutes being closed to unfiltered air flowing out of the second portionof the plurality of flutes so that air passing into one of the firstface or the second face of the media pack and out the other of the firstface or the second face of the media pack passes through media toprovide filtration of the air; and (c) wherein at least a portion of theplurality of flutes exhibit a flute width height ratio of greater thanabout 2.2 or less than about 0.45, and a media-cord percentage of atleast about 6.2%; and (d) wherein the fluted sheet comprises a pluralityof repeating internal peaks facing toward the facing sheet and repeatingexternal peaks facing away from the facing sheet, said plurality ofinternal and external peaks comprising sharp contact points withadjacent facing sheets.
 2. An air filtration media pack according toclaim 1, wherein the fluted sheet comprises repeating internal peaksfacing toward the facing sheet and repeating external peaks facing awayfrom the facing sheet, and a repeating pattern of flutes comprising atleast one ridge extending along at least 20% of the flute length betweenan internal peak and an adjacent external peak.
 3. An air filtrationmedia pack according to claim 1, wherein the sharp contact points aresufficiently sharp that the fluted media at a plurality of the internalor external peaks is sufficiently sharp so as to not be curved at thepeaks.
 4. An air filtration media pack according to claim 2, comprisinga repeating pattern of flutes comprising at least two ridges extendingalong at least 20% of the flute length between an internal peak and anadjacent external peak.
 5. An air filtration media pack according toclaim 1, wherein the first portion of the plurality of flutes are closedby a sealant bead and the second portion of the plurality of flutes areclosed by a sealant bead.
 6. An air filtration media pack according toclaim 1, wherein at least a portion of the plurality of flutes aretapered.
 7. An air filtration media pack according to claim 1, whereinthe media pack has a volume asymmetry volume so that a volume on oneside of the media pack is greater than a volume on another side of themedia pack by at least 10%.
 8. An air filtration media pack according toclaim 1, wherein the media pack has a volume asymmetry so that a volumeon one side of the media pack is greater than a volume on another sideof the media pack by about 40% to about 200%.
 9. An air filtration mediapack according to claim 1, wherein the single facer media is provided ina coiled arrangement.
 10. An air filtration media pack according toclaim 1, wherein a plurality of the single facer media are provided in astacked arrangement.
 11. An air filtration media pack according to claim1, wherein the internal peaks or the external peaks have a radius ofless than 0.25 mm.
 12. An air filtration media pack according to claim1, wherein the fluted sheet provides a media-cord percentage of about7.0% to 16%.
 13. An air filtration media pack according to claim 1,wherein the at least a portion of flutes exhibits a flute with heightratio of greater than about 2.5.
 14. An air filtration media packaccording to claim 1, wherein the at least a portion of flutes exhibitsa flute with height ratio of less than about 0.40.
 15. A filter elementcomprising an air filtration media pack according to claim 1, and a sealmember extending around a periphery of the media pack.
 16. A filterelement according to claim 15, wherein the seal member comprises a sealsurface constructed to engage an air cleaner housing surface in one of aradially extending direction and an axially extending direction.
 17. Anair filtration media pack comprising: (a) a plurality of layers ofsingle facer media wherein the layer of single facer media comprising afluted sheet, a facing sheet, and a plurality of flutes extendingbetween the fluted sheet and the facing sheet and having a flute lengthextending from a first face of the filtration media pack to a secondface of the filtration media pack; (b) a first portion of the pluralityof flutes being closed to unfiltered air flowing into the first portionof the plurality of flutes, and a second portion of the plurality offlutes being closed to unfiltered air flowing out of the second portionof the plurality of flutes so that air passing into one of the firstface or the second face of the media pack and out the other of the firstface or the second face of the media pack passes through media toprovide filtration of the air; and (c) wherein at least a portion of theplurality of flutes exhibit a flute width height ratio of greater than2.2 or less than 0.45, and a volume asymmetry so that a volume on oneside of the media pack is greater than a volume on another side of themedia pack by at least 10%; and (d) wherein the fluted sheet comprises aplurality of repeating internal peaks facing toward the facing sheet andrepeating external peaks facing away from the facing sheet, such that aplurality of the peaks comprise sharp contact points with adjacentnon-fluted sheets.
 18. An air filtration media pack according to claim17, wherein the volume asymmetry is about 40% to about 200%.
 19. An airfiltration media pack according to claim 17, wherein the fluted sheetcomprises repeating internal peaks facing toward the facing sheet andrepeating external peaks facing away from the facing sheet, and arepeating pattern of flutes comprising at least one ridge extendingalong at least 20% of the flute length between an internal peak and anadjacent external peak.
 20. An air filtration media pack according toclaim 19, comprising a repeating pattern of flutes comprising at leasttwo ridges extending along at least 20% of the flute length between aninternal peak and an adjacent external peak.
 21. A filter elementcomprising an air filtration media pack according to claim 17, and aseal member extending around a periphery of the media pack.
 22. A filterelement according to claim 21, wherein the seal member comprises a sealsurface constructed to engage an air cleaner housing surface in one of aradially extending direction and an axially extending direction.